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westing house tv works but smells of smoke

Discussion in 'Troubleshooting and Repair' started by NCC74656, Jun 6, 2013.

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  1. NCC74656

    NCC74656

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    Jun 6, 2013
    i just got this tv for free and it works but smells of smoke, i took it appart and found that it is burnt on a single chip on the power board.

    pics: what is this part i need and where can i buy it?

    http://imgur.com/a/UMd7l

    thanks.
     
  2. DuctDuck

    DuctDuck

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    Jan 26, 2013
    Hmm, not sure...but try this link
     
  3. davenn

    davenn Moderator

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    Sep 5, 2009
    its one of the step up transformers for LCD backlight. its output will be in the order of 1500V or so

    Dave
     
  4. NCC74656

    NCC74656

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    Jun 6, 2013
    got it, ill try a local shop and see if they sell this. if not ill buy it off ebay.
     
  5. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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    Nov 28, 2011
    It looks to me like the PCB has burnt up quite badly. If that's the case, you'll need to remove every bit of discoloured PCB, otherwise the problem will just recur.

    You'll need to remove the transformer first (be gentle with it), and use something like a Dremel to grind away the fibreglass PCB material until there is no darkened material left. It looks like you will also need to remake the transformer's secondary pin connection (to the capacitor and the CCFL connector) because there is charred fibreglass all around that pin.

    If the set works, you can assume that the transformer is OK and you don't need to replace it.
     
  6. NCC74656

    NCC74656

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    Jun 6, 2013
    I will check into that. the set has a couple poped caps so im going to replace those tomorrow. how can i test this transformer to see if it truly is good? i suppose this could have been a single incident of a surge but i just dont want to put a semi working part in there.

    you say i need to take off all teh burnt material, if there are no connectors or leads in an area why would it matter if it remains burnt?
     
  7. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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    Nov 28, 2011
    It wasn't a surge. It could have been an internal defect in the PCB material, or maybe a spillage on the board.

    If the display lights up properly, the transformer is OK. Have a close look at the part of it that was near the area of the burn-up though.

    It matters because of the high voltages present. Any conductive material reduces the creepage distance and can cause a new conduction path to form. See https://en.wikipedia.org/wiki/Insulator_(electricity) and search for creepage.
     
  8. NCC74656

    NCC74656

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    Jun 6, 2013
    there is a glob of something on the side of the transformer. looks like its burnt and melted.
     
  9. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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    Post a photo. Also if you've removed the transformer, post photos of both sides of the PCB in the burnt-up area, and the underside of the transformer.
     
  10. NCC74656

    NCC74656

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    Jun 6, 2013
    you can see the dot on the pictures i already posted. left side of the front of hte transformer
     
  11. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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    I see it. I don't think it's a problem. How about the other transformer? Is there any blob on that?

    I'd like to see the underside of the transformer above the burn-up. If there's no visible damage there, I wouldn't worry about the blob.

    Is it possible the blob has dripped onto the transformer from above? With the board in its original position, is there anything above it?
     
  12. NCC74656

    NCC74656

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    Jun 6, 2013
  13. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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    OK. I can't tell anything more from those pics. I would like to see the underside of the transformer, and closeups of the burnt-up area on both sides of the PCB.
     
  14. NCC74656

    NCC74656

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    Jun 6, 2013
    k, ill desolder it. couple min
     
  15. NCC74656

    NCC74656

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    Jun 6, 2013
  16. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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    Nov 28, 2011
    Yep, that's a nasty burn-up. You'll need to remove every bit of discoloured PCB and re-make the connection from the transformer secondary pin as I said in post #5.

    See if you can clean the transformer using isopropyl alcohol. Be gentle with it and hold it in a folded-up paper towel. Oil from your skin can affect the grey ferrite material if you touch it.
     
  17. NCC74656

    NCC74656

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    Jun 6, 2013
    that melted spot i saw ont eh top is directly above the pin. are we sure the transformer is still good? its got a pretty good indent where the plastic is melted on the under side.

    ok so i just touched the melted part and it fell appart. its got a good 1.5mm hole and the pin fell out. there are also 5 cracks spreading out from this hole going to 3 of the 4 sides of the transformer. i think i need to buy a new one
     
  18. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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    OK. I got a replacement CCFL transformer once from a company called lcdparts.net. They may also be able to sell you a complete inverter board, which will save you from repairing it, though it will cost a lot more than a transformer.

    The board seems to be a Darfon B070-401. That doesn't seem to be listed, but you could email them and tell them the situation, to see whether they can help.

    There are other companies who sell complete CCFL inverter boards and individual transformers. Do a Google search.
     
  19. NCC74656

    NCC74656

    42
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    Jun 6, 2013
    i have a local shop that has only electronic parts so im going there tomorrow. at the least i can pick up caps for the board. the transformer is 10 bucks on ebay but id like to get it local if i can.
     
  20. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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    Nov 28, 2011
    I doubt you'll find the transformer locally. They are a specialist component.

    Re the capacitors, if they're electrolytics, do you know if they're low ESR? If so, you'll need to replace them with low ESR electrolytics too. If you're not sure, post all of the markings and I'll look up a data sheet.
     
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